Solenoid devices that use their encasement in magnetic circuits are widely known. An exemplary version is illustrated in U.S. Pat. No. 4,004,258 Arnold wherein the encasement 12 serves as a component of two magnetic circuits 19,21. Such devices are particularly useful as valve actuators in applications which demand a latching function. A problem in such applications is that if electrical power is lost in the system used to excite the coils of the solenoid device, the position of the armature (and, by extension, the position of the valve) is fixed and cannot easily be changed without restoration of power.
The primary objective of the present invention is to provide a solution to the above-described problem.
Other objectives and advantages of the invention may become apparent from the following description, which includes the appended claims.